These days, with the application of high-level emission control regarding diesel engines (hereinafter merely referred to an engine), it has been demanded that an exhaust gas purification device for purifying and treating air pollution substances in exhaust gas is mounted in agricultural work machines or construction work machines in which an engine is mounted. As the exhaust gas purification device, a diesel particulate filter (hereinafter referred to as DPF) for collecting particulate matter and the like in the exhaust gas has been known (for example, see Patent Literature 1).